ROCs derive from the UK’s Renewable Obligation that obliges all suppliers to hold certain small percentages of ROCs as a proxy for having green electricity in their mix – this % goes up each year by about 1% and is currently approaching 10% as an annual obligation.

ROCs are widely traded separately to power. For example the Big Six are always drastically short of ROCs and seek to buy them as stand alone bits of paper wherever they can.

Good Energy are also short of ROCs which seems odd when you think that they buy 100% green electricity from the markets and their obligation for ROCs is still in single figure percentages by contrast. The reason for that is that GE buy most of their power without ROCs.

Ecotricity is long in ROCs. This year our own green energy is over 50% of our fuel mix. The 37% figure BTW is last year – all Fuel Mix Disclosure is a year in arrears – because electricity supply isn’t complicated enough… So Ecotricity has over 50% ROCs and needs less than 10% – roughly speaking.

When financing windfarms the income from selling ROCs is half the total windfarm income – it’s a vital component. That’s one reason we think retiring ROCs is a crazy self defeating idea – ROCs are designed to make windfarms economically viable, so that more get built, and they do that well. To ‘retire them’ is close to self immolation … Well it is if you’re about building anyhow.

The other reason we’re against the practice is that it achieves nothing (except false hope) – the ASA have banned the claim that ROC retirement leads to more building – because GE and others have been unable to prove it. Won’t go into more here, it’s just something that sounds good in principle but in practice it’s nonsense.

So Ecotricity uses ROCs for what they are intended. GE uses them for greenwash IMO.

It’s the customer that pays for ROC retirement though.

ROC retirement is at least part of the reason that Good Energy are the UK’s most expensive electricity supplier. Or is it?

Anthony says Good Energy claim to retire 15% ROCs – the claims made by their team on the phone do indeed vary widely up to and beyond this amount. But the actual official claim is 5% of ROCs. This is the claim that GE made to NCC and to FOE et al for the last 5 years. NCC said this explains the (hefty) premium for Good Energy.

It doesn’t though – this amount of ROCs would cost about £25 per customer whereas the premium was £80 a year when NCC wrote that. (BTW it’s only £50 as of this week)

GE has been talking about building new green sources for 10 years or so, since the day they got started in energy supply. It may well happen one day. They came up with the idea of ROC retirement because it was something they could do and they needed a green story, an edge to claim greater greenness from. It’s not more than that. It’s an all but abandoned philosophy now.

There is more to this story though, something rotten at the heart of it all – coming soon.

Moving on to REGOs – these are certificates based on an EU wide scheme to verify and demonstrate the veracity of fuel source. Each unit of green generated gets one and each unit of green sold has to have one attached to them. Fuel Mix Disclosure is EU wide law and uses REGOs as evidence of source. REGOs are sold separate to power though. And it doesn’t matter for reasons of practicality/laws of physics.

This links to my comments that basically you buy non de script power in the wholesale markets, attach a REGO and it’s green. At its simplest this is because we can’t direct the flow of electrons to our customers and the grid system is a big mixing pot. Inputs are measured and can be offset against outputs – and that’s how the system works. But specific electricity can’t be delivered, so bits of paper are used to make sure that things like greenness are only sold once.

Moving on then to how many windmills will it take to power the UK. The rough rule of thumb that I use is it takes 1,000 MW to meet that 1% annual RO increment – it’s close but not forensic BTW.

On that basis we need 100,000MW of wind to power the whole UK – not allowing for issues of demand and supply balance – just total use.

That’s 50,000 of our 2MW machines, 33,000 of today’s typical 3MW machines and only 20,000 of the 5MW machines that are now appearing and will surely dominate in the future. Turbines up to 10MW are highly likely – that would obviously only take 10,000 – the reality will be a mixture of turbine sizes of course, as we build as we go.

As to land use – Many years ago an outfit called ETSU (gov quango..) undertook a study of the UK’s usable wind resource on land – and the word usable is important. They concluded that we had enough usable sites for wind energy to meet our entire electrical needs 3 to 4 times over. That was almost 20 years ago, with 20 year old technology.

Looking at it another way – on the question of spacing turbines – we reckon that in any given land area a wind farm will occupy just 1% of the land itself – due to spacing needs. Jeffrey calculates for us here that 1% of the UK’s land is 360,000 turbines – that’s 3 to 4 times the number of turbines my rule of thumb says we need for 100%. Which chimes with the ETSU study.

The big caveat that needs adding is of course supply and demand balancing – and let’s not forget energy use reduction.

I don’t disagree with Prof McKay on the need for us to reduce energy use, but I do disagree with his apparent fixation on that to the exclusion of actually building renewable forms of power. The two things are not opposing forces – they are reinforcing – we need to use less and make what we have to use, from renewables.

If we can reduce our consumption by 50% we need just 50,000 of today’s turbines and just 5,000 of tomorrows…. The UK has 2,500 already BTW (although smaller and older types)

There will still be supply and demand to balance though even under the best reduction scenario. For that we have the concept of Intelligent Demand, forget the days of dumb ‘energy on demand’ we can run the grid and our lives more efficiently. And we will.

I believe that the UK should generate way more than 100% of its needs from wind (onshore of course) and should export and/or usefully ‘dump load’ using large scale Intelligent Demand – because the ‘longer’ we are in terms of wind capacity (compared to needs) the more of the time that we will have enough when we need it – and also because we have so much wind – why not use it.

The fact that wind is free and clean (and endless) requires a new mindset to some degree – we need not be constrained by our total annual usage, let’s build 200% or 300% wind for example – generation will match demand more often/easily and there must be many good things we can do with that (surplus) energy. Just a thought.

39 responses to “ROCs, REGOs and wind-powering GB”

Dave Howey

February 4, 2009 at 10:24 am

Dale (hallo again by the way!), you said “I don’t disagree with Prof McKay on the need for us to reduce energy use, but I do disagree with his apparent fixation on that to the exclusion of actually building renewable forms of power. The two things are not opposing forces – they are reinforcing – we need to use less and make what we have to use, from renewables.”

I don’t quite follow what you are saying here… and I don’t think MacKay says this in his book (withouthotair.com). From my reading of his book, he seems to be saying, basically:
1. How much do we need to live on now, today, without reducing any demands.
2. Can renewable energy supply this need?
3. How can we reduce our needs (efficiency etc)?
4. How can renewable energy supply our reduced needs?

the point is, bigger turbines need to be spaced further apart, so the power per unit area for wind is roughly constant, whether you use lots of smaller machines or a few bigger machines

Jeffrey Lam

February 4, 2009 at 10:51 am

Ok, so you get both ROCs and REGOs for your renewable energy. You sell all your ROCs, except for the ~10% that you are obliged to keep.
I’m not too clear about what you do with your REGOs, if anything. Is it your REGOs that allow you (legally) to claim that 50% of your energy is renewable? And for your “plus” tariff, you buy a REGO with every unit of electricity you purchase, which allows you to claim that 100% is renewable?
Presumably, GE have *no* energy production capacity of their own, they purchase the equivalent amount of energy to their customers’ demand from other (green?) suppliers. Then they buy the ~10% ROC obligation, plus 5% (allegedly) extra to retire? And they also buy 100% REGOs, allowing them to claim it is 100% renewable?
Have I understood correctly?

I’m fairly chuffed that my arithmetic using google/wikipedia figures combined with Dale’s rule of thumb chimes with the ETSU study!

ROCs or no ROCs we have to accept that green energy comes with a (relatively small) increase in cost to the consumer. However I agree that a completely market “consumer chooses to pay approach” will not work as unfortunately Jeremy Clarkson needs to be forced into paying for it (and the ROC system does this).

I disagree with Dave Howey’s comment – that Dale and McCay are on the same page. We already know the answer to 1 and 2 (lots of energy required and not enough renewable energy to supply). 3 and 4 suggest an ordered approach along a time line. Global warming is going to happen so fast and the job of reducing carbon emissions so huge that we cannot afford to take such an approach – 3 and 4 need to be combined and both happen now.

Just to confirm, I (David MacKay) advocate simultaneously doing the following things:
1) implement efficiency measures as fast as possible (Eg electric vehicles, heat pumps, insulation); AND 2) get lots and lots of green electricity supply built up as fast as possible; AND 3) make appropriate demand-balancing/storage systems to cope with demand/supply fluctuations.
I find it strange to be told that I advocate “only efficiency”. Please read my book. It is free online! Incidentally, other people seem to propagate the other (equally incorrect) view that “MacKay ignores efficiency options”. Sigh. Please read the book. If equal numbers of people propagate both these incorrect statements, does it mean I roughly got the balance of the book right?

Dave Howey

February 5, 2009 at 10:33 am

well- there you have it from David MacKay himself. I agree– if you haven’t read the book, read it first before commenting!!!

Chris

February 5, 2009 at 11:25 am

Dale, when will the latest figures for 2008 be published on whichgreen.co.uk ?

Alan Tayler

February 6, 2009 at 7:46 am

Dear Dale,

I admire what you have achieved and your green approach in general and wish you and your company well. I have emailed your company with questions on two occasions and have had absolutely no response so I thought that an approach to the man at the top might be interesting.

I read on your site that you are developing a domestic wind generator model and I simply wanted to know if this was the case still and how things are going? This does have a slight bearing on your ROCs explanations and contrasts interestingly with the situation in Germany where I believe the subsidy for micro-generation is greater than here – leading obviously to a greater take up. With the general fall in investment returns a slight tweaking of subsidies would make home generation look relatively attractive – particularly when you consider how UK energy prices are so ‘world – beating’ in the negative sense…

In relation to comments from Dave Mackay/ Dave Howey I had read some of the book when I commented. I confess I did originally skim read it and came to an early judgement as some of the initial content did not seem revolutionary and in some parts contained incomplete information e.g wind speeds generally being below 6m/s in the UK (without referring to a height above ground level or lack of context e.g. the fact that even in lower wind speed areas energy can be maximised by bigger wind turbine rotors effectively giving a similar energy output to turbines in windier areas). The references to bigger wind turbines not greatly increasing the total power output per unit land area does not reflect the “real life picture” as although wind turbines need to be spaced further apart the relative output from fewer turbines with larger blades is greater even using the same land area (given higher capture of energy through greater overall blade swept area). Other constraints such as noise (fewer larger turbines may be quieter than a larger number of smaller turbines) allow you to fit more turbines onto a site) and there are many other constraints on wind farm sites aside from the technical e.g. ecology land use, etc. Furthermore many smaller (in term of overall turbine numbers) wind farms could contain turbines closer together whilst still generating at a high capacity factor as the wake effect behind the turbine is reduced. OK – detailed points but this is a detailed book.

The scary numbers are already out there – on climate change, the scientists at the Hadley Centre have been on the case for some time and in terms of energy demand sources such as the UK digest for energy statistics have good workable figures. Responses from energy companies to government consultations have contained the clear message about the energy gap (including the numbers) and the need to do everything we possibly can (in a big way) to deal with this. These numbers have informed renewable energy targets and ultimately the tough decisions the government has to make on issues such as coal fired power stations and nuclear.

What is good about your book (having re-read the book in further detail) is the overarching agreement – we need to do everything in a “big” way. However this does not stop the need at least get the public doing the little things in terms of energy saving and renewables – it all contributes and I think this is where the message sent out by the book is being perceived differently. We do have to find a simple and effective way of getting the efficiency/ green generation message across to the public quickly and effectively. Rather than being “codswallop” for example comparisons of energy production with the number of homes equivalent at least lets people put into context what a wind farm might generate. They are not going to read a 300 page plus book about the numbers.

Vicky, thank you for reading my book, and for your positive overall reaction. You complain that the book is too long, and you also complain that when I mentioned wind speeds, I didn’t say what height the wind speed data was gathered, nor discuss the dependence of wind speed on height. Well, please make your mind up – do you want the book to be longer or shorter?! Yes, I omitted discussion of height in the three-page-long chapter on Wind http://www.inference.phy.cam.ac.uk/withouthotair/c4/page_32.shtml
because I wanted to keep the length down to three pages! But please don’t misrepresent what is in the book. I _do_ say what height the data is measured at (namely 10m, page 265) in the Chapter “Wind II” (pages 263-268). And I _do_ discuss (on page 266) the variation of wind speed with height. Finally, you assert that turbines can be packed closer together without losing power? Please provide data. (That idea would seem to contradict the Danish Wind Energy Association, who say that you get significant shadowing if the spacing is closer than 5 diameters.) I’m always keen to see new data. All the best, David MacKay.

Alexandra Deegan

February 9, 2009 at 7:06 pm

A couple of points worth noting!

China is rapidly emerging as the next global wind power. During 2008 it doubled wind energy capacity – for the fourth straight year – adding 6,300 megawatts of new electricity generation for a total capacity of 12,210 megawatts….

And in the rush to build the next gen’ hybrid cars or EV’s, a sobering fact confronts both automakers and govts seeking to lower their reliance on foreign oil: almost half of the world’s lithium, the mineral needed to power the vehicles, is found in Bolivia — a country that may not be willing to allow much access to the mineral!

I am not saying your book is too long. I am saying that different methods of spreading the word are needed for different audiences and the short messages are not necessarily as you describe in your book “codswallop”.

Thanks for your clarification on wind speed height – my key point is that there is huge potential for wind energy in the UK from a technical and commercial perspective and the success of modern turbines coupled with the ROC are to thank for this. Wind speed (and therefore viability) is not the key constraint. Neither is physical space.

It is correct that if you reduce spacing to under 5 by 3/4 rotor diameters you may reduce energy but this depends on a huge number of factors including topography and forestry and the size of the wind farm (I test this by using energy estimates from wind farm design software and actual measured anemometry data fed in – developers use this to maximise the potential of a proposed wind farm site). My point is that other factors are hindering the potential of renewables and wind energy – mainly politics at a local level. It is here that you often hear – “efficiency first”, or “we agree with renewable energy but this is not the right place” (hence my misplaced reaction to Dave Howey’s comment).

A quick question for Dale – in light of the recent Warwick Wind trials by Encraft are you continuing your domestic turbine development or are you going to target it for a specific “niche” market?

Hi Alan, don’t know what happened to your other two mails but we’re looking for them now (just to understand if we have a prob somewhere).

Meanwhile, to your questions/thoughts. Our domestic wind turbine work is indeed still ongoing, we expect to put the mark two up at out test site in a few days. We’ve made some good progress to date – our focus from here will be on a new generator and inverter set up – we seem to have the blade design nailed.

We call it the Urbine BTW – as it’s a wind turbine optimised for Urban use.

This work has no bearing on my ROC explanations though or my stance on Micro gen and Feed in Tariffs, which you can read about here.

We’re developing the Urbine because our customers kept asking us for a recommendation (mini mill wise) and we kept saying don’t touch any of them right now – then we thought we’d better use our wind knowledge to see if we couldn’t make one that actually was worth installing. That’s how it came about.

I’m actually against Feed in Tariffs – insofar as they tend to be exaggerated in their actual impact on the problem and they divert attention and funds from the real issue – big wind. I’m not against the concept of micro gen, though I have tried to shine a light on it’s economics.

The economics of big wind have deteriorated seriously with the fall of the pound in the last few months – but it’s nowhere near enough to make microgeneration a better investment or even anywhere close to being on a par – the gulf is still huge.

Hope that makes some sense.

Cheers.

Bob

February 11, 2009 at 2:04 pm

Dale

You mention the concept of “intelligent demand” (yet another phrase aka demand-side management, demand response, demand-side participation). This is very encouraging.

Given that Ecotricity has presumably the most variability in supply of any generator, it stands to benefit most from getting flexible demand from its customers. So are you doing anything in this area?

In addition to the technology/integration, to make it work we may need to completely re-write the way that smaller customers are handled. Smart Metering can provide much of the data (1/2 hourly reads), but unless we significantly alter the way that electricity is settled through the BSC and get rid of profile settlement, there will be no way to realise the value of customers using power at different times – no way for suppliers to capture value and share it with customers.

Also,have a look at the recent Daily Mail coverage of the RWE/RLtec trial (especially website comments) and you’ll see that there’s a mountain to climb there in terms of public opinion.

The evolution of the energy system to a demand-led “predict & provide” to your nirvana of a supply-led wind-powered world (a good vision) is something that will take active engagement and *collaboration* between all participants in the market- DECC, OFGEM, Big6, NatGrid, DNOs and consumers. I would be an extremely disappointed Ecotricity customer if you continued to wax lyrical about this opportunity and didn’t contribute.

It may not feel like it, but have it on good authority that many organisations listed above are taking it demand-side flexibility very seriously.

David

February 11, 2009 at 5:29 pm

Dale

Good work on what you are doing.
I just have one question and it relates to your numbers:
you say “100,000MW of wind to power the whole UK”
and
“That’s 50,000 of our 2MW machines”

Is that not a bit misleading given that you need to take into account the capacity factor, given that for Wind this is about 30% then we would need 3-4 times as many Wind turbines as you estimate.
If I am right then these things need to be clear so we on the pro wind side can not be seen to be misleading.

To David, from David MacKay: I expect Dale already factored in the load factor in his “roughly 100 GW”. UK electricity consumption today is about 45 GW on average; so (at a load factor of 30%) you need 150 GW of wind to cover it (plus appropriate energy storage systems to cope with supply and demand fluctuations). I think that if we talk about “powering the UK”, it’s good to speak about how much power is needed to provide all power, not just today’s electricity. In particular, there’s heating power and transport power (both currently fuelled by fossil fuels). If we want to defossilize both these power sources then it increases the number of windmills required by quite a bit. In my free book (withouthotair.com) I estimate how much power would be required by zero-carbon Britain. To cover not only today’s electricity but also (efficient electrified) transport and (efficient electrified) heating (using heat pumps), we would need something like 125 GW of electricity on average (more in the winters of course). This plan, I must emphasize, involves very significant energy efficiency measures compared with today. Now, If we delivered this power mainly with wind, we would need about 420 GW of wind capacity (and lots of storage). The land or sea area required for the windfarms is roughly 62,000 square kilometres. Which is roughly one quarter of the area of the UK and roughly three times the area of Wales. So yes, technically we can power the whole UK from wind alone – as long as it’s acknowledged that one quarter of the UK would be occupied with wind-farms. I’m fine with that idea. I’m not anti-wind. Just pro-arithmetic! If people don’t like having so many wind-farms they can always choose to buy **kes instead. Other options, other mixes, are sketched in the book. They all involve big building projects – there’s no way of getting away from it.

UK unrestricted peak demand is only ~65GW anyway AFAIK, so by some measures that’s too much (that peak peak demand comes in winter and correlates with more wind) and by some too little.

Given that 100% pure wind supply is unlikely to be practical, 100GW of wind is probably a reasonable stab at enough capacity ignoring balancing/backup.

Rgds

Damon

David

February 13, 2009 at 6:26 pm

David MacKay – I’ve brought and read the book cover to cover and was very impressed, it was party why I wanted Dale to be clear in his arithmetic i.e. what the numbers ment and where did they come from.

The book has increased my ambition to change career into renewable energy. I am currently studing via distance learning at Loughborough University for an MSc in Renewable Energy, I just need to find an employer and leave IT Contracting behind.

Thanks for the clarification.
David
Anyone got any jobs?
Interested in Wind and Biomass.

Alan Tayler

February 16, 2009 at 8:19 am

Interesting to see that the ROCs changes have already caused BT to abandon their wind power initiative.

Dave Howey

February 16, 2009 at 11:05 am

Dear David “The book has increased my ambition to change career into renewable energy” (there are a lot of Dave/Davids on this page – me included!).. I know someone who has done just what you want to do, his blog is here: http://peplers.blogspot.com/ – I suggest you get in touch with him perhaps. I think he did an MSc in renewable energy.
Dave Howey

BT pulling out because they have been double accounting – I wondered how they were offering such great deals to landowners for wind farms on their land. You will notice the more established wind farm developers not being affected.

Ecotricity is an exciting company and reading your website caused me immediately to apply to switch from my current supplier, Southern Electric (which I understand to be part of Scottish & Southern).

I think your sales pitch needs tidying up a smidge though (bear with me, this ends up positive :)). Your Jan 2008 Progress Report says “1 in 6 of the wind projects in England today have been planned and built by Ecotricity.” Well ok, but England is a relatively small part of what’s happening as yet and it is the quantity of generated wind power that matters to me, not particularly where in the UK it comes from. Do you disagree? I wanted to check out what you were saying and found the British Wind Energy Association UKWED database [www.bwea.com], which tells me that when your report came out there were a total of 419 active wind projects (in planning, consented, in construction or operational), of which Ecotricity had 16 (57.9MW) and Scottish & Southern had 12 (724.25MW) – a factor of 12.5 in favour of Scottish & Southern in terms of power. And yet you quote Scottish & Southern as spending zero per customer on wind. That is, at the very best, disingenuous and it doesn’t become you – you should either find a fair estimate to quote or not quote anything at all.

At this point, having applied to switch to Ecotricity, I had a very uncomfortable feeling that I had been conned.

I wanted a fairer picture of the amount of energy being generated per customer from wind, to allow a rational comparison and check my decision. Dividing the power output of the wind projects that a company is carrying out by how many customers it has gives the number of Wind Project Watts per Customer (WPWC, prounounced “WiPWaCs”). Ecotricity had 33,000 customers at the time of your report and Scottish & Southern around 5M (excluding its gas customers). This gives 1,755 WPWC for Ecotricity and 145 WPWC for Scottish & Southern – a factor of 12.1 in favour of Ecotricity.

So I’m going ahead with the switch to Ecotricity.

If you want to get the real facts over to people without danger of insulting their intelligence, this is the number you should be headlining. It shows simply and fairly the difference in companies’ commitment to wind, normalised with respect to the number of customers. Quoting absolute pounds spend per customer reminds me of the sort of thing a government might say to skate over the size of a problem:).

It’s really striking that 75% of planning applications for major developments are decided in 13 weeks but only 7% of applications for onshore wind! [www.bwea.com] What would you say are the main problems? As a Psychology graduate doing Project Management, I’m well used to working on multi-stakeholder projects constrained by regulation and standards, enforced whimsically at times. I’d like to get involved. I can think of almost nothing more satisfying than taking a wind project through from application to planning consent. An insightful article by Prof Susan Opotow on the subject of managing conflicts in environmental projects talks about how to recognise when stakeholders are not responding positively to eachother and what to do about it [http://findarticles.com/p/articles/mi_m0341/is_3_56/ai_69391499]. But looking at the planning decisions for various refused wind energy projects reveals a more complicated picture that would be very interesting to work on.

I should probably come back to you on a couple of the points you raised, because I think otherwise there’s a possible misunderstanding.

Our 1 in 6 of the windmills in England isn’t intended to deceive. England is the country we operate in, it’s where we have our entire focus, other than two industrial site projects we’ve built in Scotland.

And we believe England needs to be where the action is – that’s where maybe 80 or 90% of the population of the UK lives (haven’t checked that stat it’s a guess BTW). We believe that energy should be generated close to the point of use, and that people should live with the sources of their own generation. I don’t believe that all the windfarms should be in Scotland or Wales (and all the demand in England). It’s only been predominantly so until now because of greater windspeeds and therefore economics – but it’s shifting to England now.

Coming to the £ per customer. For whatever year you saw us quote zero pounds for SSE spent on new renewables, it will have been true. Each year we publish the figures for that year, we pass them to each supplier for correction and comment, they are real figures. What we don’t do is factor in promises of future spend. And I think you may have conflated those two things here – actual spend and future spend (which may or may not happen). We’ve been publishing these figures now for five years, they show a true picture and they expose the empty promises of the big six – so far.

We’re being neither disingenuous not dishonest with these figures – they are what they are – the actual spend of each supplier, each year.

Your WiPWaCs idea is cute. It’s a bit complicated for the average man on the street though, whereas our £ per customer is dead simple.

Actually what you’ve come up with is another way to express fuel mix – the % of green (in this case) that each supplier has. Of course it should because you divide wind units generated (a proxy for green electricity) by customer numbers (a proxy for total demand volume).

Our fuel mix this year is about 50% from self built green sources. Most of the big six will struggle to reach 5%. That’s just another way to represent it. We’re about ten times better on that measure and about 12 on your WiPWaCs – close enough to be the same thing given my ‘fag packet’ numbers.

But £ per customer measures the rate of change – it demonstrates the doing of something that grows generation and hence green %. Rate of change is everything.

£ per customer cuts to the heart of the issue. The UK has about 5% green in its national mix, the only thing that really matters is how fast we build the next 50% – spending per customer shows each of us where our choice of electricity company can have most impact.

You ask what’s the biggest hold up to more new capacity – it’s the planning system without doubt. Wind is the only energy source in the hands of local councils for planning consent and it’s no co incidence it’s the only one with such planning hassle.

Funding has actually just become perhaps a bigger obstacle, though it will pass shortly I feel. The credit crunch has hit renewables now, very few banks are willing to lend and in all cases they will lend far less of a projects total cost – there’s a debt gap in renewables right now (more of that later maybe). But I expect it’ll lift in a year or so.

Building is without doubt the best bit.

Glad to have you as a customer and thanks for this.

Cheers.

Adam

April 2, 2009 at 12:12 am

A Question…

If you were to leave 30 million electric cars (with their battery packs) parked and hooked up to the grid most of the time, to what extent could that provide demand balancing for wind energy distribution? What percentage of wind penetration would be fesable assuming normal driving and charging patterns for the cars?

Guys, a few thoughts from me (and answers) on this thread. (sorry for the slowness….:)

On ROCs and REGOs first. Jeffrey and Anthony ask what happens to Ecotricity’s REGOs – the answer is nothing. We keep them. They prove the fuel source of our supply.

Jeffrey you have it about right – Good Energy, for example, would get LECs and REGOs for each of the units of green they buy (that’s what the market insists on) and hence would have 100% to claim 100% greeness with – but they would only get the ROCs they fork out for or self generate – and self generation might be only 10%.

And the 5% ROC retirement is soo ‘allegedly’ as you say. We’ve been digging into this for a few weeks and just can’t get a straight answer from Good Energy. OFGEM figures say something all together different…..more on this later.

On Micro wind – Vicky, the results of the Warwick Wind trials hasn’t affected our work on the Urbine, it just confirms what many of us held to be true – that urban winds are pretty rubbish and the current crop of machines likewise. We don’t know if the Urbine will make widespread use of urban winds viable, or if it will be a more niche type application – but we’re aiming to make a machine that makes the most of the winds in urban locations – if that’s not good enough to be viable, fair enough.

There’s one other thing I feel worth a mention. On the subject of Codswallop (don’t get to hear that term too often)

From reading the thread it appears that David (MacKay) in his book claims that you cannot get more capacity of wind power out of any given land area, by simply increasing the turbine size. The reason offered is that as turbines get bigger, the blades get bigger and therefore they need spacing further apart. That much is true but it overlooks something.

The amount of energy you can extract from the wind (with a turbine) is directly proportional to the swept area of the blade (the area of the circle the blade sweeps). This area is driven by the length of the blade of course (the radius of the circle) – but the area swept follows a square law – pi R squared. Whereas the spacing required between turbines does not, it’s linear.

Here’s an example to illustrate – let’s say a blade is 10m long, its swept area is 100 pi – its spacing requirements are say 5 x diameter (across the wind) so 5 x20 = 100m.

If we use instead a blade of 20m, its swept area is 400 pi – its spacing requirements are 5 x 40 or 200m.

Swept area and therefore energy capture increases fourfold, spacing requirements, just double. Therefore, roughly speaking, you’d get half as many machines making four times as much energy – giving double the production capacity for any given area of land.

That’s the theory. I asked our wind team to verify this by setting standard layouts for a small machine (800kW) and a large one (3MW) – in one square km of land.

Not a doubling of generator capacity, but I think that’s to do with the fact that we used of two different manufacturers machines – and they all size blades to generator capacities differently.

Energy yield would be the ultimate comparison, haven’t had time to run that though…… But clearly, you do get many more MWs installed capacity in any given piece of land if you use bigger machines. The theory says twice as much due to the square law fighting the linear one.

Hi Jeffrey, can of worms this one…. A LEC is a Levy Exemption Certificate, it’s awarded to qualifying units of renewable generation, OFGEM are the gatekeeper again but the recipient or beneficiary of the scheme is actually HMRC. There’s a tax on primary energy use called the Fossil Fuel Levy, it applies to all forms of energy including electricity – but only for business, not for domestic use. Business electricity users basically pay a tax of about 0.4p per unit of electricity they use. Technically it’s the suppliers that pay the tax, but of course they pass it on or build it in, but it’s their liability, like VAT. If as a supplier you hold LECs, you can use them in lieu of the tax. Thus 0.4p is added to the value of renewable energy, via the fact that (most of) it qualifies for the LECs. Hope that makes sense. Cheers.

Jeffrey Lam

April 27, 2009 at 6:18 pm

Thanks Dale. That does make sense. Cheers.

Jeffrey Lam

April 14, 2009 at 11:27 am

I’ve got questions on your turbine spacing too. Yes there is a linear relationship between spacing requirement and blade length, but does that not lead to a square relationship between the amount of area needed and the blade length?

Let’s say we have four turbines in a square formation (I suppose they won’t be arranged in a square, but I’ll come to this later). One turbine in the SW corner, one due east from the first, one due north from the first and one NE from the first. If the spacing is “L” then the area required is L squared. What if we double the blade length? The capacity increases four-fold. The length L doubles. So now the SE turbine is a distance 2L east of the the first turbine, likewise the NW turbine is 2L north of the first turbine. The total area? 2L x 2L = 4L squared, a four-fold increase.

But I imagine you use a triangular formation. And as I’m typing I don’t know what the answer will be. The area of an equilateral triangle of length L is 0.5 x (L squared). We double the blade length, quadruple the capacity and double length L. We get 0.5 x 4 x (L squared): a fourfold increase. Ok, now I think about it, the area increase is fourfold regardless of the formation. Actually, one exception: if all the turbines are in a single line. In that case it is only a doubling in the amount of area (effectively) needed.

But that contradicts the results of your wind farm optimisation software. Have I done something wrong?

Hi Jeffrey, there’s definitely an impact from layout (shape), as you say, and straight line would def be the optimum to max out the square law effect. Shape may be one factor behind the difference between the purely theoretical result I first got to and the one our optimisation software spat out – they were quite different.

But nonetheless the software does show increasing capacity from bigger machines (on the same example site), although capacity is not the whole story, annual yield is really what the theoretical approach goes to – because the amount of potential energy capture follows the square law relationship between increase in blade length and swept area. Haven’t examined that yet but some work we’re doing on a site right now shows that tower height can increase yield significantly – so there’s another variable.

Cheers.

Jeffrey Lam

April 27, 2009 at 6:33 pm

Thanks Dale.
I think what I was trying to say is that my crude calculations suggest that it is not a square law fighting a linear one, but a square law fighting another square law!
Unless the turbines are strung out in a straight line. As soon as you introduce the second dimension it should be square law versus square law in my mind.

But if the optimisation software results are real and correct then I will happily concede to them… I’d just like to know why I’m wrong.

Hi Jeffrey, I’m not saying you’re wrong, and I don’t think you are actually. I can see what you’re saying. Wind farms don’t often follow a regular shape, either square or linear. especially the larger ones – and this is probably why the answer from the software is somewhere below the ‘pure theory’ (if I can call it that) of square law versus linear, and somewhere above the competing theory of square versus square – the actual layout modelled in this case is probably the explanation. Real world layouts can be quite messy. All sorts of factors come in to play, like microwave links and other zones to be avoided. Hope that helps. Cheers.

Jeffrey Lam

May 5, 2009 at 8:26 pm

Thanks Dale. I was just thinking about what I said anyway. I guess in real life it’s more complicated than any law. Furthermore, if a wind farm needs a certain amount of area it doesn’t mean that the turbines between them occupy every square inch of that area… looking at the Lotus wind farm artist’s impression, I can see that the three turbines are sharing the space with the Lotus site buildings!

What I was going to say was that in reality many of your wind parks are one or two turbines, meaning the area they need doesn’t change or is the square law fighting the linear law. But when the turbines are in among other buildings etc. such as at Lotus, or at Worksop, or in Reading, or Dagenham, then it is a completely different story anyway. You don’t need to set aside significant amounts of land for wind-parks like these, as the land is being used anyway. I suppose you can’t put the turbines too near to residential areas, but other than that you don’t need to exclude land from being used for the sake of turbines.

Zero Carbonista

This blog is about answers to the big questions - how will we keep the lights on, what kind of cars will we drive (will we drive?) and how will we feed ourselves - in a post oil world, and a world where we can't afford to keep burning things and throwing things away. Energy, Transport and Food are the three big issues.